1. Field of the Invention
The present invention relates to a method for manufacturing an inflatable ball, and more particularly to a method that makes the inflatable ball with excellent quality in a simplified and economical way. The inflatable ball made by this method is also disclosed.
2. Description of Related Art
A conventional inflatable game ball, such as a basketball, is basically composed of an inner bladder, a winding string layer forming around the bladder, an intermediate layer formed around the winding string layer, and a cover attached over the intermediate layer. Typically, the cover is achieved by attaching multiple panel pieces made of leather or artificial leather. In order to make the attachment of the panels easy and precise, the intermediate layer (so-called carcass) is formed around the bladder by pasting multiple thermoplastic rubber pieces on the winding layer with the bladder. Because the intermediate layer is made of rubber material, the inflatable bladder has to be vulcanized in a mold with heat and pressure to improve elasticity of the intermediate layer. Because the mold has multiple internal embossment patterns defined on an inner periphery of the mold, therefore, the intermediate layer is formed to have marking lines or channels corresponding to the embossment pattern for precisely arranging the panels on the intermediate layer. Additionally the outer surface of the intermediate layer has to be roughened to make the attachment of the cover panels secure. Lastly, the panels are manually attached around the intermediate layer.
According to the above description, manufacturing a conventional basketball is very troublesome and time-consuming, especially in the acts of forming the intermediate layer, vulcanizing the intermediate layer, roughening the intermediate layer and attaching the panels. Although there are several prior patents modifying conventional methods for manufacturing the basketball, the methods in those prior patents still have drawbacks that are illustrated as follow:
A first prior patent, U.S. Pat. No. 6,123,633 (hereinafter referred to as '633 patent), disclosed a game ball comprising a carcass and a plurality of cover panels secured to the carcass. The carcass has a lobular outer surface that is provided by a plurality of generally spherical portions, channels between adjacent spherical portions of the carcass, and recessed portions between each channel and the adjacent spherical portions. Each cover panel has a central portion secured to one of the spherical portions of the carcass and a side portion secured to one of the recessed surface portions. Each of the cover portions has a substantially uniform thickness of less than 1.25 mm and the central portions of the cover panels extend radially outwardly beyond the channels (see claim 1 and FIG. 3 of '633 patent). The basketball in '633 patent apparently shows the intermediate layer that is numbered as “34” in FIG. 3 and is formed by pasting multiple sheets of rubber so as to thermally mold into the intermediate layer (see column 3, lines 8 to 16).
Therefore, disadvantages of forming the intermediate layer still exist in '633 patent. Additionally, the cover panels 21 are extremely thin, about 0.031 inch (0.8 mm), whereby the cover panels 21 wrinkle easily when the cover panels 21 are coated with adhesive or secured on the intermediate layer 34. Manufacturing the basketball in '633 patent requires much time and skill, especially in the attachment of the cover panels 21.
A second prior patent, U.S. Pat. No. 5,931,752 (hereinafter referred as '752 patent, disclosed a basketball with a laid-in channel or logo basically having a carcass, a plurality of panels of cover material and pieces of laid-in material. The carcass has an inflatable bladder covered by an integral outer rubber layer 18 made by the same manner of '633 patent (see column 3, lines 3 to 12 and FIG. 4 of '752 patent). The plurality of panels of cover material is secured to the carcass while some portions on the carcass are not covered by the cover materials. The pieces of laid-in material have good grippability and are secured to the bare portions without overlapping the cover materials.
Therefore, disadvantages of forming the intermediate layer 18 (i.e. the rubber layer) still exist in '752 patent. The panels of cover material 12 are usually thin whereby the panels 12 wrinkle easily when the panels 12 are coated with adhesive or secured on the intermediate layer 18. Manufacturing the basketball in '752 patent still requires much time and skill, especially in the attachment of the panels 12.
A third prior patent, U.S. Pat. No. 5,681,233 (hereinafter referred as '233 patent), disclosed a basketball comprising an inflatable bladder, a layer of windings over the bladder, a plurality of panels of sponge rubber formed over the layer of windings, a plurality of strips of rubber, and panels of cover material, wherein the carcass of the basket ball excludes the panels of cover material (see column 2 lines 18 and 19). Although the intermediate layer is changed in name in '233 patent, the flat sheets of panels of sponge rubber 16 perform the intermediate layer as shown and described above by molding. In other words, the intermediate layer is the same as in the two prior patents. Moreover, it is noted that the rubber channel 13 is achieved by attaching and thermally molding two strips of rubber 17, 18 to form a bulged rubber channel 13 before the panels of cover material are attached to the carcass (see column 2, lines 20 to 40). The rubber strips 17, 18 are vulcanized into the underlying wound bladder and are thereby integrated with the wound bladder. The cover panels 12 are bonded or integrated with the rubber strips (see column 2, lines 47 to 50).
Apparently, the intermediate layer still exists and disadvantages of forming the intermediate layer remain in '233 patent. Manufacturing processes of '233 patent are complex because each layer and strip of rubber has to be thermally molded or vulcanized in different molds. Therefore, manufacturing basketball of '233 patent is troublesome, time-consuming and expensive.
With regard to a fourth prior art, a U.S. patent application Ser. No. 10/395,666 (hereinafter referred as '666 patent), disclosed a method for manufacturing a basketball comprising acts of: preparing an inflatable spherical bladder; surrounding the bladder with a winding string layer; respectively preparing a rubber sheet and a polyurethane sheet; combining the rubber sheet and the polyurethane sheet and then cutting them into multiple panels with desired shapes; attaching the multiple panels to the winding string layer to compose a basketball; and vulcanizing the basketball. Particularly, pebbled periphery of the basketball are formed in correspondence with an engraved pattern on an inner surface of molds when the basketball is heated in the mold for vulcanization.
According to the manufacturing acts in '666 patent, the basketball still has the intermediate layer (i.e. the rubber sheet). Therefore, thermal vulcanizing act is unavoidable if the rubber sheet is to be elastic and durable. Because the pebbled periphery of the basketball is molded inside the mold with the engraved pattern, the basketball can not be flexibly changed to various patterns unless the mold is changed to have different engraved pattern. Moreover, although the intermediate layer is previously attached to the polyurethane sheet (34, i.e. the cover material) to make the panels become thick enough to attach on the winding string layer easily, some temperature sensitive materials (such as logo foil) are easily deformed and decolored by heat in the vulcanizing act (about 150° C.). Therefore, the basketball has limitations in the application of the commonly used “temperature sensitive” materials on it surface.
To overcome the shortcomings, the present invention is focused on a method for manufacturing an inflatable ball having excellent quality in simplified procedures to mitigate or to obviate the aforementioned problems.